package day07;

import java.util.Random;

/**
 * 需求：生成？位验证码（大写字母、小写字母、数字）
 */
public class VerificationCode {
    public static void main(String[] args) {
        String code = generateVerificationCode(4);
        System.out.println("验证码为："+code);

    }
    public static String generateVerificationCode(int len){
        String code = " ";
        char[] chs ={'a','b','c','d','e','f','g','h','i','j','k','l',
                     'm','n','o','P','q','r','s','t','u','v','w','x',
                      'y', 'z','A','B','C','D','E','F','G','H','I','J',
                      'K','L','M','N','O','P','Q','R','S','T','U','V','W',
                       'X','Y','Z','1','2','3','4','5','6','7','8','9','0'};
        Random rand = new Random();
        for (int i = 0;i<len;i++){
            //int index = (int)(Math.random()*chs.length);
            int index = rand.nextInt(chs.length);
            code+=chs[index];//验证码拼接
        }
        /**
         *  i = 0; index = 1;  code = "d"
         *  i = 1; index = 4;  code = "e"
         *  i = 2; index = 45; code = "T"
         *  I = 3; index = 60; code = "9"
         */

        return code;
    }
}
